Method for hydrolyzing chlorosilanes and preparing polysiloxane resins



Patented Sept; 21, 1949 mo m nvnnouzmo mono-- raaranmo rousmoxann nesms Harry F. Lamoreaux, Ballston Lake, N. 2., aaaignor to General Electric Company, a corpora- SILANES- AND tion of New York No Drawing.

The present invention relates to novel p siloxane resins and toa method of preparing such polysiloxanes. It is particularly concerned with an improved process of hydrolyzing mixtures of chlorosilanes having a hydrocarbon-to-silicon ratio greater than 1 and not more than 1.5 and including a major portion oi methylchlorosilanes.

It is well known that organohalogenosilanes, or mixtures thereof which may also contain some silicon tetrahalides, readily hydrolyze when mixed with water to form silanols which condense ltical purposes the condensation of the silanols occurs simultaneously with the hydrolysis of the chlorosilanes. Because both reactions occur instantaneously, the hydrolysis of methylchlorosilanes containing a sufllcient number of chlorine atoms attached to silicon to form heat-hardenable products by mixing them with-water results in the formation of insoluble gels which cannot be used in the manufacture of useful resinous compositions or in the formation of products of low average molecular weight rather than the high average molecular weight products-sought in the preparation. of resinous products in general.

Variousinethods have been devised for con trolling the hydrolysis reaction and the earlier attempts along this line had for their principal object the prevention of gel formation during hydrolysis. However, as more and more knowledge accumulated concerning the various methods of hydrolysis, it became apparent that certain methods not only permitted the carrying out of the hydrolysis without using ice or ice-water mixtures for the more readily hydrolyzable chlorosilanes but also resulted in the formation of polysiloxanes having properties markedly difierent than those of the earlier known polysiloxanes which had the same general formula and were prepared from the same chlorosilane mixtures. It thus appears that the polysiloxanes, particularly those obtained by the cohydrolysis and cocondensation of mixtures of two or more chlorosilanes, will differ from one another,-depending on the conditions of hydrolysis and condensation, in much the same way that other resinous materials, such as the .phenol formaldehyde condensation products, difler from one another depending upon theconditions under w ich the Application November 21, 1945, Serial No. 630,135

'1 cam. (01. 260-455) resin forming reactions are caused to take place.

One of the earlier methods for controlling the hydrolysis of methylchlorosilanes is described in Rochow Patent 2,258,218 and comprises dissolving the chlorosilane mixture in ether and adding the resultant solution to ice or a mixture of ice and water. Another process is described and claimed in the copending application S. N. 455,617 filed August 21, 1942 (now U. S. Patent 2,398,672, issued April 16, 1946) in the name of Robert 0. Sauer and assigned to the same assignee asthe present invention. The'Sauer process comprises the solution of the-chlorosilanes in a solvent such as toluene and the addition to this solutoin to a mixture comprising water and a, higher alcohol such as butanol. Although the prior methods resulted in the formation of liquid, heat-hardenable producta'the'y also involve certain disadvantages. Largevolumes of solvents were usually necessary and in some cases the resinous products possessed poor craze resistance. Certain of the methods did not lend themselves.v either to the easy separation of the solvents or the-recovery of the hydrogen chloride byproduct, both of which are essential in any large scale commercial project.

The present invention is based on the discovery that improved polysiloxane resins can be obtained by partially hydrolyzing a mixture of hydrocarbon-substituted chlorosilanes including a major portion of methylchlorosilanes, heating the partially hydrolyzed products in order to remove most of the hydrogen chloride dissolved .therein and thereafter completing the conversion of the chlorosilanes to polysiloxanes by adding enough water or ammonium hydroxide to complete their hydrolysis.

It has been found that diethylene oxide and the diethers of ethylene and diethyl glyco1 serve as excellent solvents or mediums for the hydrolysis of the chlorosilanes, particularly methyl and phenyl chlorosilanes, or mixtures of the two. This type of solvent includes dioxane, diethyl Ce1losolve (bis,(beta-ethoxyethyl)ether) and diethyl Carbitol (ethylene glycol diethyl ether).

The invention is particularly concerned with the formation of methyl andmethyl phenyl poly-,- siloxanes from mixtures of methylchlorosilanes including a major portion of methyltrichloro silanes or mixtures of methyl and phenyl chloro silanes containing a major portion of methyltrichlorosilane, phenyltrichlorosilane, or the mixtures of the two. Ordinarily, the water employed for the partial hydrolysis of the chlorosilanes will be in an amount ranging from about 50 to about .80 per centof that calculated as necessary for complete hydrolysis of the chlorosilanes. Stated alternatively, on a molar basis, since it is evident that for complete hydrolysis of a chlorosilane, at least 0.5 mol water may 'be employed in eilecting complete hydrolysis of each gram atom of chic-- rine, to efl'ect from 50 to 80 per cent hydrolysis I Example 1 A solution of 100 g. methyltrichlorosilane and 80 g. dimethyldichlorosilane in 200 g. dioxane and 50 g. mineral spirits was placed in a flask provided with a reflux condenser, stirrer and dropping funnel. 20 cc. of water was added dropwise to this solution. The reaction mass was agitated fairly well during the hydrolysis. At completion of the partial hydrolysis, the reaction mass was refluxed to remove the bulk of the absorbed hydrogen chloride, 2 hours usually being asumcient reflux time. When the mass had cooled to about 80 degrees 0., cc. of water was added rather rapidly and the reaction mass again heated to refluxing. By having the hydrolysing equipment so constructed to include a small trap and draw-on? tube just below the tip of the reflux condenser, the dioxane was then drawn-ofl until the temperature of the remaining resin solution reached 140 degrees C. The resin solution was removed fromthe hydrolyzer and n1- tered.

At this pointthe resin solutlons may retain small quantities of hydrogen chloride which, if

desired, can be removed by addinganelkaline material such as calcium oxide, sodium carbonate, etc, and reflltering or by adding the neutralizer directly'to the hydrolyzed mass before the initial filtering. A

The cured films of the resinous product of Example 1 were harder and tougher than films of previously known polyailoxane resins" prepared from the same chlorosilane mixture.

Example 2 Employing the same equipment as that described in Example 1, a mixture of 100 g. methyltrichlorosilane, 60 g. dimethyidichlorosilane and 20 g. diphenyldichlorosilane dissolved in 200 g. of

'diethyl carbitol were partially hydrolyzed by the dropwise addition of 20 cc. water. The partially silane, 100 g. dimethyldichlorosilane and 39 a. silicon tetrachloride dissolved in 200 8. diethyl Cellosolve was partially hydrolyzed by the addition of 20 cc. of water. The hydrogen chloride dissolved in, the partially hydrolyzed pro'duct was removed by fractionation, after which 10 cc. of

' water 'was added to complete the hydrolysis of 1. The method of preparing a polysiloxane resin which comprises partially hydrolyzing a mixture of monovalent hydrocarbon-substituted chlorosilanes including methylchlorosilanes having a hydrocarbon-to-silicon ratio of at least one and not more than 1.5 by adding to a solution of said chlorosil'ane mixture in a polyether solvent a quantity of water less than that calculated asnecessary for complete hydrolysis of the chlorosilanes, heating the resultant product to remove a major portion of ,the hydrogen chloride dissolved therein and thereafter adding sufllclent water thereto to complete the conversionof the chlorosiianes to polysiloxanes.

2. The method of preparing a polysiloxane resin which comprises forming a solution of a mixture of monovalent hydrocarbon-substituted chlorosilanes containing a major portion of methylchlorosilanes and having a hydrocarbonto-silicon ratio of at least one and not more than 1.5 in a polyether' solvent, adding to said solution a quantity of water less than that theoretically necessary for complete hydrolysis of said chlorosilanes, heating the resultant/product to remove at least most of thehydrogen chloride dissolved therein and thereafter adding sufficient,

water to complete the hydrolysis of the chlorosilanes.

3. The method of making a polysiloxane resin which comprises dissolving methyltrichlorosilane and dimethyldichlorosllane in a mixture of dioxane and mineral spirits. partially hydrolyzing said chlorosilanes by the addition of water to said.

solution in an amount ranging from about to about 80 percent of that calculated as necessary for complete hydrolysis of the chlorosilanes, heating the resultant product to a temperature suflicient to remove most of the hydrogen chloride dissolved therein, and thereafter adding additional water to complete the hydrolysis of the chlorosilanes.

.4. The method of preparing a polysiloxane resin which comprises partially hydrolyzing a mixture of methylchlorosilanes including methyltrichlorosilane having a methyl-'tossllicon. ratio of at least one and not more than 1.5 by adding to a solution of said methyl chlorosilanes in a co polyether solvent a quantity of water less than hydrolyzed chlorosilanes were then heated to the refluxing temperature of the solution to remove the bulk of thehydrogen chloride. The addition. of 10 cc. of water completed the hydrolysis of the chlorosilanes after which the solvent was removed under vacuum and the remaining resin dissolved in toluene to form a polysiloxane var- I in Example 1, a mixture of 41 g. methyltrichlorothat calculated as necessary for complete hydrolists of the methyl chlorosllanes; heating the re. sultant product to remove a major portion of the hydrogen chloride dissolved therein and thereafter adding suflicient water thereto to complete the conversion or the chlcrosilanes to polysiloxanes.

5. The method or preparing a polys ox ne F resin which comprises forming a solution of a nish having properties similar to the product 01. mixture of Wmn'subsflmted polyether solvent, adding to said solution a quantity of water-less than that theoretically necessary for complete hydrolysis of said chlorosilanes, heating the-resultant product to remove at least most of the hydrogen chloride dissolved therein and thereafter adding sufli clent water to complete the hydrolysis of the chlorosilanes.

6. The method of making a polysiloxane resin which comprises dissolving a major portion of methyitrichlorosilane and a minor portion of dimethyldichlorosilane in a mixture of dioxane and mineral spirits to form a solution of chlorosilanes having a monovalent hydrocarbon-to-silicon ratio of at least one and not more than 1.5, partially hydrolyzing said chlorosilanes by the addition of water to said solution in an amount ranging from about 50 to about 80 percent of the water calculated as necessary for complete hydrolysis of the chlorosilanes, heating the resultant product to a temperature suflicient to remove most of the hydrogen chloride dissolved therein, and thereafter adding additional water to complete the hydrolysis of the chlorosilanes.

7. The method of preparing a, polysiloxane resin which comprises partially hydrolyzing a mixtin-e of chlorosilanes including-a major portion of methyl chlorosilanes and having a monovalent hydrocarbon-to-silicon ratio of at least one and not more than 1.5 by adding to a solution of said chlorosiianes in a polyether solvent a quantity oi water ranging from about to about percent of that calculated as necessary for complete hydrolysis of said chlorosilanes, heating the resultant product to remove most of the hydrogen chloride dissolved therein and thereafter adding suflicient water thereto to complete the hydrolysis of the chlorosilanes.

HARRY 1". LAMOREAUX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

